Process for the removal of deposit formers



United States l atetit 3,309,310 PROCESS FOR THE REMOVAL OF DEPOSITFORMERS Blanchard L. Mickel, Munster, Ind., assignor to Standard OilCompany, Chicago, 11]., a corporation of Indiana No Drawing. Filed Apr.30, 1964, Ser. No. 364,015 8 Claims. (Cl. 208255) This invention relatesto a process for the removal of certain deposit formers from reformate.

The results from tests have consistently indicated that when thegasoline endpoint is increased, some undesirable eifects occur in theinternal combusion engines in which these gasolines are being burned.These undesirable effects include increased deposits, increased octanerequirement, surface ignition, and dilution of the crankcase lubricant.

The tendency of hydrocarbons to form deposits in engines is related toboth the boiling point and type of the involved hydrocarbons. There aretwo types of deposits that occur in an internal combustion engine: thosedeposits which are found in the induction system and those which existin the combustion chamber. Recent evidence suggests that the polycyclicaromatics apparently are associated with the harmful constituents of thehydrocarbons. In fact, it has been suggested that the compounds whichform deposits in the induction system of an internal combustion engineare polycyclic aromatics which have incorporated polar groupings. Thesepolar groupings cause the particular compound to separate from the bulkof the reformate at the conditions which exist in the induction system.In no way is this suggested theory presented here to limit the utilityof my invention. The compounds which cause these deposits, whatever theymay be, will hereinafter be referred to as deposit formers.

The inclusion of heavy aromatics from the various reforming processes ingasolines has been economically attractive. The consumer of thesegasolines, which contain the so-called deposit formers, must beprotected from the effects of such compounds. There are several ways toachieve this protection, and in one of them the harmful compounds areremoved completely by physical separation processes; in the other,special gasoline additives are used to partially counteract the harmfuleffects of the deposit formers. Deposit formers may be removed byconventional re-running of the reformate. Re-running is the process ofremoving a small percentage of the heaviest portion of reformate bydistillation. This is a sound method for removal, but its cost is highand the accompanying loss in gasoline volume is appreciable. besubjected to the re-running treatment, but in such a case, the feedendpoints might be more restricted than they would be if conventionalre-running were used. Furthermore, the re-running process is notselective of the materials being removed with regard to performance inengines. Consequently, the removal of a greater percentage of thereformate bottoms might be necessitated to provide adequate protectionfrom the most harmful portion of the deposit formers. The specialgasoline additives which are used to counteract the harmful effects ofthe deposit formers would not completely prevent further build-up of thedeposits.

My invention provides a relatively inexpensive method of selectivelyremoving the deleterious deposit formers A portion of the totalreformate couldthat exist in high-severity r'efo rmate. High-severityreformate is the product that is obtained from a reforming process thatis being operated at a high temperature and a low pressure to furnishvery high octane material. The process of my invention comprises thepassing of the high-severity reformate, hereinafter called reformate,through a bed of material such as glass beads, sand, gravel, slag andcoke at conditions which permit at least 98-99% of the hydrocarbons toremain in the vapor phase as they pass through the bed of small inertparticles. The material making up the bed of small inert particlesshould be chemically inert with respect to hydrocarbons. The temperatureof the surface of the inert particles is less than the condensationtemperature of the heavy deposit-forming compounds, but greater than thevaporization temperatures of the, other constituents of the reformate.The pressure of this system should be maintained at a fairly low valuesince more heat is required to vaporize the hydrocarbons as the pressureis increased. As the hydrocarbon vapors move through the bed ofparticles, the undesirable heavy deposit formers condense and the liquidso formed adheres to the surface of the packing. The effluent reformatevapor, from which the deposit formers have been removed, passes onthrough and out of the column, is condensed and stabilized, and may beblended directly into motor gasoline without any further processing being required to reduce the deposit-forming tendencies of the product.

The reformate may be introduced into the packed column at the top of thecolumn and pass downward through the bed of small inert particles, or itmay be introduced into the column near the bottom of the column and passupward through the bed of particles. In this latter case, the heavymaterial, which will tend to collect at the bottom of the bed, may beremoved from the column periodically.

The deposits which adhere to the finely divided packing must, from timeto time, be removed from the packing. This removal may be brought aboutby oxidative regeneration. As an alternate method of providing cleanpacking, the spent packing may be removed periodically from the columnand replaced with fresh packing.

In another embodiment of my invention, reformate is contacted with airprior to its introduction into a column which is packed with materialsuch as glass beads, sand, gravel, slag and coke. This contacting withair may be performed by permitting the reformate to stand in a tank andbe exposed to air, or it may be accomplished by bubbling air throughreformate in a tank. It is possible that the air might be injected intoa stream of hydrocarbon as it passes through a line or pipe. In anyevent, it should be pointed out that such contacting and the subsequenthandling of the air-contacted hydrocarbons should be done with the aidof techniques which are consistent with current safe practices known tothose skilled in the art.

The deposit formations, which are caused by polycyclic aromatics havingincorporated polar groupings and their associated compounds and whichcan be prevented by the use of my invention, occur in the inductionsystem of internal combustion engines. Such deposit formations,hereinafter called deposits, may be studied conveniently in a laboratorybench apparatus which is referred to as the Rotogurn. This apparatus isdiscussed in detail in US. Patent 3,108,468. In the carrying out of thetest Patented Mar. 14, 1967 wherein this apparatus is used, 100 ml. offuel is slowly injected onto the walls of a rotating, inclined, heatedglass tub during a 40-minute test period. The glass tube is heated to atemperature in the range between about 350 and 400 F. Light ends arecarried out of the tube in a stream of air and gasoline bottoms remainin the tube and form varying quantities of adherent deposits. Thesedeposits are removed and weighed at the end of each test. Deposits foundin the Rotogum test may be conveniently expressed as milligrams ofdeposit per 100 milliliters of fuel tested. The deposit-formingperformance of gasolines in the Rotogum test have been correlated withtheir behavior in the intake manifolds of laboratory test engines. ThisRotogum test is very sensitive to changes in reformate tail-endcomposition.

The polycyclics found in Rotogum deposits are more dependent uponhydrocarbon type than upon their original concentration in gasoline.Aromatics such as anthracenes and pyrenes are predominant in Rotogumdeposits even though their concentration in gasoline is very low. Thefollowing table illustrates an example of the distribution of thepolycyclics from a reformate in the hydrocarbon portion of the Rotogumdeposits.

Approximate percent Hydrocarbon: in deposit Pyrenes 30 Anth rac enes 2 1Naphthalenes 4.5 Diphenyls 4 Acenaphthenes l a-Phenyl-naphthalenes 12.5Chrysenes 13 Others Pyrenes comprise about 30% of the hydrocarbonsfound, and are the predominant aromatic. The next most prevalentaromatic, anthracenes, comprise about 20% of the hydrocarbons.Hydrocarbons that boil higher than anthracenes or pyrenes were found insmaller quantities in these deposits. The relative contributions ofthese aromatics to the formation of intake-system deposits in engineshave not been established.

Example I This example illustrates the effectiveness of my invention inremoving the deposit formers from a reformate, whether the reformate istreated immediately after it has been produced in the reformer orwhether it has been permitted to stand for a period of time in a storagetank. For convenience in the laboratory, the liquid reformate wasintroduced into the column at its top and the initial portion of theheated packed bed was used to preheat the reformate. This column, whichhad a volume of approximately 100 ml., was filled with 3 mm.-diameterglass beads. The column was heated along its entire length and wasmaintained at a maximum temperature of 650 R, which was the temperatureof the treated reformate as it exited from the column. The vapors of thetreated reformate were condensed and collected at a rate of about 200mil. per hour. Three dilferent reformates were treated in this manner.The first, referred to as reformate A, was purged with nitrogen prior toits passage through the packed column. The second and third were made upof reformate B. The second reformate was purged with nitrogen prior toits passage into the packed column while the third was contacted withair prior to its passage into the packed column. For each of thesereformates, 100- ml. samples were periodically withdrawn from thematerial as it exited from the packed column and were tested in theRotogum apparatus. Prior to treatment in the packed column, reformate Awas found to yield a Rotogum deposit of 5.5 mg. per 100 ml.; reformateB, a Rotogum deposit of 11.0 mg. per 100 ml.; and air-contactedreformate B, a Rotogum deposit of" 11.0 mg. per 100 m1.

AirCoutacted Reformate B Reformate A Reformate B No bottoms other thanthose which adhered to the glass-bead packing were removed from thereformate. These results show a substantial reduction in thedepositforming tendencies of the reformate after it has been passedthrough a bed of samll inert particles and a further reduction if thereformate has been contacted with air prior to its passage through thepacked column.

Example 11 This example illustrates the effectiveness of removingdeposit formers from a reformate by passing the reformate through a bedof gravel. The particle size of the gravel varied from about A3" toabout A" in diameter. Testing was performed as above and the value ofthe Rotogum deposit obtained with reformate prior to its treatment was11.0 mg. per 100 ml.

Total volume passed Rotogum deposits,

through column, liters: mg./ 100 ml. 1 3.0 2 2.7 3 3.6 4 5.0

These results show that the deposits were appreciably reduced when thereformate was passed through a bed of gravel.

Example III This example illustrates the elfectiveness of removing,deposit formers from a reformate by introducing the reformate at a pointon the column containing the packingwhich is somewhere between themiddle of the colu't'n'rr and the bottom of the column. In this case,the inlet to the column, a glass tube which was about two feet long andhad a diameter of 18 mm., was located so that 18 inches of the packing,glass beads, were above the inlet and 4 inches of glass beads were belowthe inlet. At the bottom of the column was a stopcock, an outlet throughwhich the heavy liquid which contained deposits could be removedperiodically from the column. At the top of the column was a side armthrough which the vapor was discharged into a condenser. A collectionvessel was placed below the outlet of the condenser and received thecondensed, treated reformate'. T reformate to be treated was chargedinto the colum at the inlet at a rate of one liter per hour. The coitlmtemperature was maintained at 650 F. by means of an electrical tapeheater wound over its entire length. A thermometer was placed at the topof the column so that the vapors rising out of the packed bed wouldsweep past the thermometer into the condenser. The temperatures of thesevapors ranged from about 450 F. to 500 F., values which were above theendpoint of the reformate. With this method, almost gallons of reformatewere treated. Only 0.34% of the charged reformate was withdrawn throughthe stopcock as hottoms. This removal was done on a semi-continuousbasis. The following data were obtained from samples taken from thefirst 25 gallons charged to the system. The Rotogum deposit resultingfrom the untreated reformate was 11.0 mg. per ml.

The results of this example clearly demonstrate the efieetiveness ofremoving deposit formers by introducing the reformate at a point nearthe bottom of the packed column and permitting the treated reformate topass up through the packing while removing, from time to time, the heavydeposits from the bottom of the column. A very clean reformate isobtained. Furthermore, a larger quantity of reformate can be treatedbefore the packing in the column must be regenerated or replaced.

A further understanding of my process may be gained from the followingproposed installation. Reformate, obtained from either the high-pressureseparator of a reformer or from a storage tank, passes through a lineinto a furnace Where it is heated to a temperature that is above theendpoint of the reformate as determined by ASTM distillation methodD-86. The heated reformate then passes from the furnace into one of twoparallel packed columns at a point near the bottom of that particularcolumn. The appropriate piping and valves connect the furnace to thecolumn so that the heated reformate will be introduced into only one ofthe columns at any given time. The other column is maintained as aspare. Each of the columns is packed with one of the followingmaterials: glass beads, coke, sand, gravel and slag. The heatedreformate passes up through the packing of the column being used. Theheavy deposit formers in the reformate adhere to and-are retained on thesurface of the packing. Some of this heavy liquid descends through thehead to the bottom of the column where it is collected and removedperiodically from the system through a line and a valve. The remainderof the reformate, still in the vapor phase, continues onup through thebed and out of the column into a condenser. An appropriate system ofpiping and valves connects the column to the other column and thecondenser. Operation of the proper valves above and below the columnrestricts the flow of the reformate through only one of the packedcolumns at a time. The reformate is condensed in the condenser andpasses therefrom through a line into a stabilizer where the light endsare separated from the rest of the reformate and sent from the top ofthe stabilizer through a line, perhaps back to the reformer. Thestabilized liquid product is removed from the bottom of the stabilizerthrough a line to gasoline-blending facilities.

There are two parallel packed columns in this installation so that whenpacking of the column in use has become spent, that is, the heavydeposit formers adhering to the packing surface have reduced itseffectiveness in the removal of the deposit formers, the alternateparallel column can be placed in service While the spent packing in theoriginal column is either regenerated or removed and replaced with freshpacking. Another reason for the dual columns is that if the temperaturedifferential between the surface of the packing in the column in serviceand the hydrocarbon vapors passing therethrough becomes so small thatthe column will not effectively perform its function, the alternatecolumn can be used while the temperatures in the first column are beingreduced.

If the reformate is obtained from a storage tank, it will have beencontacted with air through exposure as a result of not beinghermetically sealed in the tank. Of course, air can be bubbled throughthe reformate being stored in the tank prior to its subjection to theprocess for removal of the deposit formers.

The above examples are presented solely to illustrate my invention andthey are intended in no way to limit the scope of my invention.

What I claim is:

l. A process for the removal of deposit formers from a reformate whichcomprises the passing of said reformate through a bed of small inertparticles at conditions which permit at least 9899% of said reformate toexist in the vapor phase as it passes through said bed, the temperatureof the surface of said particles being less than the condensationtemperature of said deposit formers and greater than the vaporizationtemperatures of the other constituents in said reformate.

2. Process of claim 1 wherein saidbed is made up of a material which isa member of the group which consists of glass beads, coke, gravel, sandand slag.

3. Process of claim 1 wherein said reformate is introduced into the topof a vertical column containing said bed and is passed down through saidbed.

4. Process of claim 1 wherein said reformate is charged near the base ofa vertical column containing said bed and is passed up through said bed,the heavy deposits which collect at the base of said bed being removedtherefrom periodically.

5. A process for the removal of deposit formers from a reformate whichcomprises contacting said reformate with a molecular-oXygen-containinggas and subsequently passing said reformate through a bed of small inertparticles at conditions which permit at least 9899% of said reformate toexist in the vapor phase as it passes through said bed, the temperatureof the surface of said particles being less than the condensationtemperature of said deposit formers and greater than the vaporizationtemperatures of the other constituents in said reformate.

6. Process of claim 5 wherein said bed is made up of a material which isa member of the group which consists of glass beads, coke, gravel, sandand slag.

7. Process of claim 5 wherein said reformate is introduced into the topof a vertical column containing said bed and is passed down through saidbed.

3. Process of claim 5 wherein said reformate is charged near the base ofa vertical column containing said bed and is passed up through said bed,the heavy deposits which collect at the base of said bed being removedtherefrom periodically.

References Cited by the Examiner UNITED STATES PATENTS 1,780,977 11/1930Leslie et al. 208364 2,848,379 8/1959 Rehner et al. 20899 3,085,9724/1963 Krane et al 208-99 DELBERT E. GANTZ, Primary Examiner.

SAMUEL P. JONES, Examiner.

1. A PROCESS FOR THE REMOVAL OF DEPOSIT FORMERS FROM A REFORMATE WHICHCOMPRISES THE PASSING OF SAID REFORMATE THROUGH A BED OF SMALL INERTPARTICLES AT CONDITIONS WHICH PERMIT AT LEAST 98-99% OF SAID REFORMATETO EXIST IN THE VAPOR PHASE AS IT PASSES THROUGH SAID BED, THETEMPERATURE OF THE SURFACE OF SAID PARTICLES BEING LESS THAN THECONDENSATION TEMPERATURE OF SAID DEPOSIT FORMERS AND GREATER THAN THEVAPORIZATION TEMPERATURE OF THE OTHER CONSTITUENTS IN SAID REFORMATE.